What are the supported media file types?

These are the actual file name extensions the player can read. For example, the player will see and display a file called abc.jpg, but if you rename it to jpg.abc it will become invisible to the player and you will not be able to display it. ".abc" is not a supported file name extension. It is important to note that many of these filetypes are container formats, which means that they can contain a variety of codecs, not all of which are supported.
These file types are currently supported:

AVI (or MKV or DIVX) are the type of container. They are supported. But the video inside the container must be of a supported video codec or you won't get any video. The audio inside the container must be of a supported audio codec or you won't get any audio.

Is there a maximum number of media files the player can see?

Previous OPPO Digital players had a limit on the number of media files they could see on disc or USB storage. I don't know if there is a limit on this player, but if so it is much larger. I have been told that media with "thousands" of files have been tested.

Does it play high-definition divx/xvid and mpeg files?

Is AVCHD video supported?

Yes, on both disc and USB.
The AVCHD directory name must be all capital letters as shown, but can be within any subdirectory, meaning you can have a collection of AVCHD directories on one disc or USB device.
See the directory layout in the AVCHD wiki article.

Does it support .iso disc images as data files?

No.
The chip maker balked at this due to copy protection concerns. Apparently "iso" means "illegal content" to the industry.

How do I return to the browser in the same folder when playing a video file?

Why don't all media video files show attributes in the browser?

...but for other container types it shows nothing. I don't know why, but presume each container type has it's own API and development for each type has to be prioritized.

Why are media file names not sorted alphabetically?

It's a bug. Files are shown in their physical ordering on the device, which is usually their creation order. Some mp3 players and other devices exhibit the same non-sorting behavior.
Here are some utilities that will sort the files on a USB FAT device correctly (use at your own risk! make backups first!):

Are data discs with long file names supported?

Yes, with some restrictions.

For a disc created with ISO9660 version 2 (ISO-9660:1999) the player will show 207 characters of directory names and 120 characters of file names (by scrolling).

A disc created with the joliet long file name extension will show 103 characters of directory and file names (by scrolling). The file name limit is actually 99 because you need 4 characters for the "." + extension.

Note

Regarding the joliet long file name extension, the Linux documentation says:

Allow Joliet filenames to be up to 103 Unicode characters, instead of 64. This breaks the Joliet specification, but appears to work. Use with caution.

Are DVD directory structures on USB devices supported?

No. Individual .vob files are supported but DVD directory structure is not, meaning the supporting information found in the .ifo files is missing.
When playing .vob files:

there are no chapters

there may be no total time or time remaining

subtitles can be strangely colored

transition between .vob files will not be seamless

Can the player be used as a media server?

No, not really. It is nice that the player supports USB devices and some containers and codecs, but for a media server you would want:

files larger than 4GB

.iso files

DVD directory structures

more containers and codecs

network devices

...and no doubt other things

Large file sizes (above 4Gb)?

Are there any plans, such as via a firmware upgrade, to support a filesystem (such as NTFS, or UFS, or EXT2 -- anything) in your USB-readers, that would allow files larger than 4Gb? Some of our HD travel videos are very big and I'm loath cut them. This is also the single negative point among Amazon's reviews of your players...

It is my understanding, that your players run some sort of Unix inside (Linux? BSD?), so it should already be possible to use something better than FAT on the USB-media. Can you, please, confirm this?

Player uses a mini-OS shell for higher functions which are proprietary to our own operation. Player does not have a full OS required for emulation of Unix functions such as NTFS formatting. This is a limitation of the design of the player and can't be adjusted through a future firmware release.

The way around this limitation is to use DLNA streaming. Your host device is responsible for filesystem compatibility - Nathaniel Plain

Of course, formatting and writing NTFS is not easy, but simply reading an already existing NTFS can not be very hard...

What DLNA-servers have you tested against? I already have MediaTomb configured (used to stream to an Archos-5 player as well as to a Windows computer), but my Sony Bravia TV, for example, refuses to work with it... Will your devices fare any better?